250.53(B) Question - IAEI Florida Chapter

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#2413 - 03/14/06 11:30 AM 250.53(B) Question
Bryan Holland Secretary Registered: 10/05/04 Posts: 1622 Loc: City of North Port	250.53(B) basically states that the electrodes of one system are to be spaced not less than 6' from electrodes of another system. It then goes on to say that when electrodes are bonded together, they become one system. Does this mean that once I bond the electrodes of two different systems together, the 6' rule would no longer apply since I now have one system? For example, I install a ground rod for the service and a ground rod for lightning protection. Since I plan to bond these two together, must they remain 6' apart or are they now one system? _________________________ Bryan P. Holland, MCP
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#2414 - 03/14/06 12:30 PM Re: 250.53(B) Question
Anonymous Unregistered	I agree you have made one system. You are still not getting the biggest bang for your grounding rod buck if they are less than 6' apart. ("well of influence" and such)
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#2415 - 03/14/06 03:02 PM Re: 250.53(B) Question
Mike Timpanaro Post-A-Holic Member Registered: 04/10/01 Posts: 1104 Loc: Ocklawaha FL.	All electrodes bonded together form one single electrode system, and the 6ft rule also applies. To get the biggest bang for your ground rod buck they need to be spaced 16ft apart . If installed less than 16ft, the grounding resistance is changed very very little. _________________________ Michael J Timpanaro Inspector/Plans Examiner/CEU Instructor Florida
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#2416 - 03/14/06 03:30 PM Re: 250.53(B) Question
Nick Sasso Post-A-Holic Member Registered: 11/08/01 Posts: 1451 Loc: West Palm Beach	Just to clarify, this 6' rule only applies to the electrodes in A5 and A6. A ground rod of one system, for example, does have to be 6' or more from a ground rod of another system. This article is talking about two distinctly different grounding systems. Possibly when there are multiple services on a building? Or 2 separate buildings very close to each other? The article that requires the 6' separation for rods on the same system is 250.56. Agree or disagree? _________________________
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#2417 - 03/14/06 03:34 PM Re: 250.53(B) Question
Mike Timpanaro Post-A-Holic Member Registered: 04/10/01 Posts: 1104 Loc: Ocklawaha FL.	Yes you are 100% correct, I should have explained that better. _________________________ Michael J Timpanaro Inspector/Plans Examiner/CEU Instructor Florida
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#2418 - 03/14/06 05:26 PM Re: 250.53(B) Question
Nick Sasso Post-A-Holic Member Registered: 11/08/01 Posts: 1451 Loc: West Palm Beach	Mike if you get a moment can you explain where the 16 feet apart comes from? _________________________
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#2419 - 03/15/06 06:13 AM Re: 250.53(B) Question
Bryan Holland Secretary Registered: 10/05/04 Posts: 1622 Loc: City of North Port	I submittted this proposal for the 2008 NEC. From what I unbderstand it has been accepted by the CMP: Quote: 1. Section 250.53(A) 2. New Text 3. Add to the end of the end of the section: Where more than one rod or pipe electrode are used for the same system, the distance between electrodes shall not be less than the length of the longest rod or pipe and not exceed four times the length of the longest rod or pipe. 4. Substantiation: 1. I feel section 250.56 should be deleted completely. (proposal already provided for this) 2. The spacing requirements in this section only applies to rod, plate, and pipe electrodes installed to meet this section. There is no requirement for electrode spacing under any other purpose for the same system. 3. 250.53(B) spacing requirements only apply to electrodes of different systems. 4. One of the primary purposes of electrical system grounding is to limit the voltage imposed by lightning as indicated in 250.4(A)(1). Per the NFPA 780 section A.4.13.2.4, "No benefit is gained from the second ground rod if placed closer than the length of the longer rod. No additional benefit is gained if the second rod is placed over four times the length of the longer rod." _________________________ Bryan P. Holland, MCP
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#2420 - 03/15/06 05:55 PM Re: 250.53(B) Question
Mike Timpanaro Post-A-Holic Member Registered: 04/10/01 Posts: 1104 Loc: Ocklawaha FL.	The ground shell area around a 8ft rod is 8ft. The farther the shells are from the electrode the lower the resistance. This is called the effective resistance area. If you install a 2nd rod in the same 8ft ground shell area as the first it does nothing..so if you have 2 8ft rods they should be spread 16 ft. _________________________ Michael J Timpanaro Inspector/Plans Examiner/CEU Instructor Florida
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#2421 - 03/15/06 07:06 PM Re: 250.53(B) Question
Nick Sasso Post-A-Holic Member Registered: 11/08/01 Posts: 1451 Loc: West Palm Beach	Thanks Mike, for that explanation. Neat stuff, Bryan. Sort of cleans up both sections and puts it all in one place. My only comment would be -- how can the inspector tell what size ground rod is installed on a given installation when he gets there to do the inspection? Be neat if there was a way to put specific distances in the proposal. For what it's worth, just my 2 cents. _________________________
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#2422 - 03/15/06 08:14 PM Re: 250.53(B) Question
Mike Timpanaro Post-A-Holic Member Registered: 04/10/01 Posts: 1104 Loc: Ocklawaha FL.	The problem......the code only requires 6ft. Once the second rod is added we don't have to meet 25 ohms. _________________________ Michael J Timpanaro Inspector/Plans Examiner/CEU Instructor Florida
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#2423 - 03/16/06 05:19 PM Re: 250.53(B) Question
Anonymous Unregistered	Mike, the way it was explained to me is that well of influence decreases as you move away from the rod as a function of the square of the distance. At 6 feet the effectiveness has decreased enough from the first rod that there is an effect from the second. I do agree farther is better but rods are simply a poor choice in the first place.
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#2424 - 03/18/06 06:51 AM Re: 250.53(B) Question
Mike Timpanaro Post-A-Holic Member Registered: 04/10/01 Posts: 1104 Loc: Ocklawaha FL.	Very True....just that driving a 2nd rod 6ft from the first is useless for lowering grounding resistance..but meets code. _________________________ Michael J Timpanaro Inspector/Plans Examiner/CEU Instructor Florida
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